Control-circuits for telephone systems.



F. "ALDENDORFF'.

CONTBOECIRCUITS FOR TELEPHONE SYSTEMS. APPLICATION FILED MAR. 16'. 1914.

1,223,304 v Patented Apr. 17;"19172- I E 2 SHEETS-SHEET 1.

wiinesses: Inveninr:

F. ALDENDORF'F.

CONTROL CIRCUITS FOR TELEPHONE SYSTEMS.

-APPUCATION FILED. MAR. 16. 1914.

Patentd Apr. 17, 1917'.v

'2 SHEETS-SHEET 2.

wihlesses-f QMW FRITZ ALi'JEnnonEE, or wuiaEnsno E, BERLIN, GERMANY.

CONTROL-CIRCUITS Eon TELEPHONE SYSTEMS.

Specification of Letters Patent.

Patented Apr. 1'7, 1917.

Application filed March 16, 1914. Serial No. 825,103.

To all whom it may concern:

Be it known that 1,.Farrz ALDENDoRrr, a

' subject of the King of Great Britain, residchange and in which the switches in the exing at 32 Mannheimerstrasse, \Vilmersdorf, Berlin, Germany, have. invented certaln new and useful Improvements'in Control-Circuits for Telephone Systems, of'ivhich the following is a specification.

My invention relates to circuits for controllingelectromechanical switches in automatic or semi-automatic telephone systems and its object is to provide an improved form of two-wire system, or in other words an improved form of the kind of system in which only two conductors extend from the telephone stations or subscribers to the exchange are controlled by the circuit loop formed of the two conductors without the aid of a third conductor such as an earth or common return conductor.

The invention consists in so arranging the circuits of the quick acting line relay of the circuit shifting or change over relay and of the release relay by which a calling subscriber controls the switch or'switches through which a Wanted connector is estab- 1 ished, that the release relay and the change 'over relay (the relay which efiects the changing over? from the selecting action to the trunk-hunting or testing function in a selector or connector) are energized during the time in which the armature of the quick acting relay travels from its back to its front contact and vice versa. The release relay is only denergized when the brief that the release and change over relays do not find time to allow theirarmatures to fall back. The release relay and change over relay are arranged to perform the releasing and change over function respectively when their armatures fall back. By a proper adjustment of the contacts of the line control relay the periods'of deenergiza- During the tion of the release and change over relay during the oscillations of the line relay armature can be made so brief that'even ordinary relays may be depended on to hold their armatures steadily attracted during the oscillations'of the line relay in the manner required of the release and change over relays Special slow acting relays or relays responding to currents of difl erent strengths as used in previously known two-wire systems may, therefore, be dispensed with in my system.

s The release and change over relays in my system may be energized by opening paths of low resistance by which the said relays are ordinarily short-circuited. The opening of these short circuits is executed by a line control relay.

As the release and change over'relays are energized by opening short circuits it is clear. that the battery circuit supplying the current flowing through the short circuits must be closed before the line control relay commences to act. In order to prevent any waste of current while the system is not being used,"the battery supply circuit for each 'set of switchcontrolling relays comprising -a line control relay, a release relay and a change over relay is closed the moment the particular relay set-is taken into use by a calling subscriber.

In the system proposed the combination of circumstances that produces the closure of the change over circuit consists in the energization of the line control relay and the simultaneous de'e'nergization of the change over relay,.the de'e'nergization of the latter relay being caused by its being shortcircuited when the former .relay is. energized. In a practical system it will happen that the line control relay will be connected to a calling subscriber (c. 9. through a line finder or trunk finder) and energized for an appreciable time before the subscriber commences working his impulse transmitter. The combination of circumstances that produces the closure of the change-over circuit would thus be set up before the changingover from the selecting action (0. g. stepping I the wipers of a Strowger selector up to the required contact row) to the trunking action (e. g. rotary trunk hunting movement of the wipers of a Strowger selector) is necessary or permissible. I overcome this difliculty by providing a contact in the change over ciring omitted as their representation is unnecessary for the clear comprehension of the invention.

In Fig. 1 S is a subscribers station which is furnished with an impulse transmitter I T and connected by wires a, 6, through the contacts 1 2 of the test relay C Rv to the line relay L R of the trunk finder. O S, is an off-normal switch which is open onlywhen the trunk finder is in its normal position and 0 S is an off-normal switch the conmots-35., 40 of which are closed only in the normal position and the contact 34 of which is open only in the normal position.

In Fig. 2 C R is a line control relay which, wheneverthe connector is used, is switched in the circuit including the calling sub scribers loop, C R, is a change over relay, R R a release relay, S M a side switch or circuit changer magnet, S, S, are movable contacts controlled by the circuit changer magnet both contactsbeing shifted from one stationary contact to the next each time a current impulse is sent through the circuit changer magnet, L M is the lifting magnet of the connector which, to simplify the description, is assumed to be of the wellknown up-and-around type, R M is the rotary magnet, R M, the release magnet of the connector, T R, is a test relay, R R, a

ringing current cut-off relay, R C R a ringing control relay and 0 S 0 S, off-normal switches that are open only in the normal position of the connector. E R is an energizing relay which closes the energizing circuit of the change over and release relays C R, a nd R R at a suitable moment and-only when the connector is taken into use. a,, 2),, 0 are wires which connect the subscriber S to the fixed contacts in the contact banks of the group of connectors through which the subscriber is accessible. 41),, '00,, w, are .the wipers of the connector.

The manner in which the system operates will now be explained.

The subscrlber S desirmg a connection raises his receiver from its switchhook and connects the wires a, Z) in a well-known Y manner thus forming a loop through a, b

2, b, S, a, 1, L R to the negative pole; The line relay L R then closes its contact?) and the turning magnet R M (which acts upon the wipers w,, wgw, in the well-known manner by a ratchet and pawl device) is alternatively energized. and denergized by current impulses flowing from the positive pole through interrupter I, R M, 3 to the negative pole. The turning magnet thus causes the wipers '20,, w,, w, to brush past the fixed contacts connected to the trunks leading to the connectors, each trunk comprising three conductorsa 1),, 0,. During the movement of the wipers the test relay T R, the circuit of which was closed at 4 by the energization of the line relay L R, tests the condition of the trunks and as soon as a free trunk is reached the test relay is excited by a current flowing from the negative pole through 4, T R, 5, w 0,, relays E R, 6 to the positive pole of the exchange battery. The relays T R and E R are energized. T R disconnects the line relay from the calling line by opening its contacts 1, 2 so that the line relay L R is deenergized and opens the turning magnet circuit at 3, which results in the wipers w,, 10,, w, stopping on the free trunk. By the energization of the relay T R the calling subscribers line a, b is extended through 8 and 9 to the wipers 1.0,, 10,. Through the contact 10 a part of the winding of the test relay T R is short circuited which causes the potential on the test wire 0, to be lowered and the trunkseized by. the trunk finders. to appear engaged to other trunk finders searchin for a free trunk. At contact 11 the test re ay T R closes a locking circuit for itself that is independent of the contact 4 which is now open. By connecting the negative pole of the battery through contacts 34, 11 and the winding of the test relay to the test wire a, coming from the connectors the calling line is made to appear engaged to all connectors through which connections to the calling line are attempted to be established as will be more fully explained later.

The moment the line relay L R was energized the negative pole of the battery was connected through the contact 4 and through T R'to the test wire 0, so that the calling line was made to appear engaged immediately the calling line commenced with the call, for as will appear more clearly later, a connection can only be made with a subscriber S when the positive potential predominates on his test wire 0,.

lVhen the relay E R was energized in the manner described above it closed the energizing circuit of the changeover relay C R, and the release relay R R. The change over relay G R, is energized immediately by a current flowing from the positive pole But the winding of the relay R R is short I the positive pole through C R, (1,, Sfla,

menced.

S, 1),, 10,. 71,, C R, to the negative pole. The relay C R then opens the short circuit of the relay R R at 8 and closes a short circuit about the change over relay C R at 12, this relay being now dcenergized while the release relay R R closes the stepping or measuring circuit of the connector at 16 and opens release circuit at 18.

The function of the change over relay C R is to shiftorchange over the stepping or measuring circuit (positive pole, 7, 14, 16 5,), which is controlled by the line control relay C R, from the lifting magnet to the rotary magnet and then to changeover the connector from its'rotary action to its testing action. As far as the invention is concerned the character of the actions taking place before and after the change over function is of no importance as the invention has to do with the change over itself and the means for accomplishing the change over may be used for changing over from any kind of action to any other kind of, action.

The change over is accomplished at the end of eachseries of stepping or measuring impulses (by, which the amount of movement of a switch or connector is determined) whenever the front contact 15 of the line control relay is kept closed for an appreciable period of time. It will happen in the practical working of the system that when acalling subscriber is connected by his trunk finder Fig. 1 to the next switch Fig. 2 the line control relay OR in this switch will be energized and its contact 15 closed for an appreciable time before the calling subscriber commences working his impulse transmitter I T and sending in the selecting,

impulses. In order to prevent a change over by this first long closure of the contact 15 the change over circuit (positive pole, 7, 15, 17, 0 8,, S M, negative pole) is kept open at 0 S until this contact 0 S is closed which does not happen until the first selecting action of the switch or connector has com- Therefore, when the change over relay C R is deenergized by the short circuit of appreciable duration at the contact 12 ofthe line control relay and the contact 17 is closed by this deenergization, the change over impulse, which would flow through 7, 15, 0 S and through the changeover magnet, is prevented by the contact 0 S being open.

Upon the subscriber S now working his impulse transmitter I T he causes in a wellknown manner a number of openings of his line loop a, b .that corresponds to the number of the wanted line and at each opening the line control relay C R lets its armature drop back so as to close the contact 14 and open the contact 12 The contacts 8 and 12 are so adjusted as to "be hardly closed during the oscillation of the armature of C R and so that if they are closed at all the closure will only take place when the armature is in its extreme rear or front position. The contact 1-1 is so adjusted as to be closed rather early in the course of the travel of the armature of C R from its forward to its back po- The closures of contact 14 result in, energizations of the lifting magnet L M sition.

by current impulses from the positive pole through 7, 14, 16, S,, L M to the negative pole of the battery, whereby the wipers 10,, w w are lifted to a contact row containing the wanted line.

On account of the above-described adjustment of the contacts 8 and 12 the short circuitings of the relays C R and R R during the oscillations otthe armature of the line control relay are so brief in duration that these relays do not find time to release their armatures during the time the selecting impulses are being sent. Therefore the contact 16 will be kept closed and the contact 17 opened during this time. At the finish of the first series of selecting impulses the line control relay C R will keep its armature attracted steadily for an appreciabletime so that the contacts 15 and 12 will be kept closed, The latter contact will short circuit and denergize the change over relay C R and then as soon as this relay allows its armature to fall back so as to close the contact 17 a change over current impulse will flow from the positive pole through 7, 15, 17, O S which Was closed the moment the wipers 10,, w w were lifted, and through the circuit changer magnet S M to the negative pole of the battery. The circuit changer magnet then moves the movable contacts 8,,

.8 into their second positions onto the conlifting magnet L M to the rotary magnet R M and upon the calling subscriber now working his impulse transmitter I T asec- 0nd time rotary impulses will flow from the positive pole through 7, 14, 16, 8,, R M to the negative pole whereby the rotary magnet R M is caused to turn the wipers 10,, M7 w around until they reach the set of bank contacts connected to the wanted line.

Vhen the rotary selecting impulses cease the line control relay C R is again energized steadily and the contact 12 is closed for an appreciable time so that the contacts 17 and 15 are closedsimultaneously and the circuit changer magnet S M is energized and moves the movable contacts S S into their third positions and closes the circuit of the test,

dered engaged and the test relay T R in the connector trying to establish a connection will not be energized because both ends of its winding will be connected to the negative pole of the battery (through S 31, 21,

and 34, 11, T R, 0 respectively).

If the wanted line is free its test wire (similarto 0 will be connected through its test relay (similar to T R Fig. l) and through parts similar to 33, 32, 0 S resistance 36 to the positive battery pole and therefore, when the circuit changer contact S Fig. 2, shifts intoits third position. a current will flow from the negative pole through S 31, 21, T R, 33, 32, 0 S 36 to the positive battery pole. The relays T R and T R will attract their armatures the latter disconnecting the line relay L R of the wanted subscriber from the wanted line and closing a newpath fromthe positive pole through 35, 11 and the former connecting the ringing current source R M to the wanted line through R C R, 27, 26 and short circuiting a part of its winding at 28, thereby immediately lowering the potential on the test wire 0 of the wanted line and rendering it engaged 2'. 6. making it impossible for other test relays T R of other connectors to be energized on connecting to the same wanted line.

Ringing current will now flow from the ringing machine R M through R C R, 27,

26, ca a: a, wanted subscribers bell, b, Z2 e0 23, interrupter 37 to the other pole of the ringing machine R M WVhen the wanted subscriber responds to the call by raising his receiver from its switchhook the ringing current flowing through the ringing control relay is strengthened sufficiently to energize this relay causing it to close its contact 22 andto energize the ringing cut-off relay R R by a current which flows from the posi tive pole through 22, R R to the negative pole of the battery. The relay R R closes 1ts contacts 24, 25 and cuts off the ringing machine R M by opening its contacts 23, .26. The relay R R closes a locking circuit for itself through its armature 38, this locking circuit extending from the negative pole through R R 38', 0 S to the positive pole and being independent of the contact 22. The calling subscriber is now connected to the called subscriber through a, 8, 10,, a 0 0 25, 10 a and a of the called subscriber,

6 b, of this subscriber and through 20 24:, 6 2, n e:

When the calling subscriber replaces his receiver and thus interrupts the connection between his line limbs a. and b for an appreciable period the release relay R R is steadily short circuited by the contact 8 and allows its armature to drop back. The release circuit at the exchange is then closed at 18 and the release magnet is energized by a current which flows from the positive pole through 0 S release magnet R M 18 to the negative pole. The release magnet remains energized until the wipers e0 10 w, return to their normal position when the off normal switch 0 S is opened. While the wipers are returning to their normal position the release magnet keeps a contact 21 open and thereby prevents the .test or busy potential being momentarily applied to the lines the bank contacts of which the wipers touch in returning to their normal position.

By opening a contact 20 the release magnet interrupts the circuit of the relays T R and E R. E R thereupon opens the circuit of C R, at contact 7 and T R closes the circuit of the turning magnet RM at 38 which extends from the positive pole through. I, R M, 39, 0 S 38 tothe negative pole of the battery. The turning magnet R M then steps the wipers w m w around until they reach their normal position in which the contact 0 S is opened and breaks the turning magnet circuit.

WVhile the wipers w 10 w, of the trunk finder are being moved into their normal positions the test circuit leading from the positive pole through 36, -10, 32, T R, 0 is kept open at 40 in order to prevent the possibility of the relay T R being energized and the trunk finder stopped by a subscriber interrupting 1 to make a connection to the partly released line through a connection Fig. 2. If the trunk (1 b 0 upon which the partly released trunk finder were thus irregularly stopped just happened to be in use, this irregular stoppage of the trunk finder wipers would result in three or four parties being interconnected.

I claim 1. In a switching system for interconnecting lines, a current source, a selector for selecting and testing said lines, a selecting relay for controlling the selecting function of said selector, an oscillatory armature on said selecting relay having back and front positions an electromagnet that isenergized the moment the armature of the said selecting relay leaves its front position and a circuit for initiating-the testing function of said selector, which circuit is rendered operative by the deenergizing of said electromagnet when'the said oscillatory armature remains over relay.

. 4. In a switching system for interconnectmg llnes, a current source, a selector for selecting a line and for changing its electrical condition, a selecting relay for controlling the selecting operation of said selector, an oscillatory armature on said selecting relay having back and front positions and an electromagnet for controlling the operation of the said selector by which it changes the condition of-a selected line,said electromagnetbeing energized by said current source in the period during which thearmature of the said relay travels from its front position to its back position.

5. In a switching system for interconnecting lines, a current source, a switch for performing operations of different characters,

I a relay for causing the said switch to perform one operation, an electromagnet for causing the said switch to change from one operation to another operation, an oscillatory armature on said relay having back and front positions, said-electromagnet being energized by said current source in the period during which the armature of the said relay travels from its front position to its back position. I

6. Ina switching system for interconnecting lines, a current source, a switch for performing operations of different characters,

-a relayfor causing the said switch to perform one operation, a front contact on said relay, an electromagnet for causing sald switch to change from one operation to an other operation, a contact member for engaging with said front contact, an electrical connection between the one end of the wind ingof the said electromagnet and the said front contact and another electrical connection between the other end of the said wind-- 1 ing and the said contact, member.

7 In a switching system for interconnecting lines, a current source, a switch for seswitching function, a selecting. circuit forcontrolling the selecting operation of said switch, a change over circuit for changing the switch from its selecting operatlon to another switching function, a change over relay with a back contact for controlling the change over circuit, a selecting relay with front and back contacts, said selecting circuit being closed through a back contact of the selecting relay and thawinding of the said change over relay beingshort circuited whenever the selecting relay closes its front contact.

8. In a switching system for interconnecting lines, a current source, a selector for selecting a line and for changing its electrical condition, a selecting relay for controlling the selecting operation of said selector, an oscillatory armature on said selecting relay having back and front positions, an electromagnet for controlling the operation of the said selector by which it changes the condition of a selected line, a circuit including the said current source, the said electromagnet and a normally open contact which is closed only whenever the said selector is taken for use, and a shunt of low resistance which deprives the electromagnet of current whenever the said armature is in its extreme front position.

9. In a switching system for interconnecting lines, a current source, a selector, a se- .said back armature contact is closed.

10 In a switching system for interconnectlng llnes, a current source, a switch performlng operations ofdifi'erent characters,

a relay for causing the said switch to repeat a certain operation, an electromagnet for causing thesaid switch to change from one operation to another operation, a restoring circuit for restoring said switch to its normal position, an oscillatory armature on said relay having front and back positions,

ashunt of, low resistance which is closed aboutthesaid electromagnet when the said armature is in its front' position and means for closing the said restoring'circuit when the oscillatory armature remains in its back position.

'11.'In a switching system for interconneoting lines, a current source, a switch for performing operations of different charac- -ters, a controlling relay for controlling the amount of an operation pe rformed by the ondary circuit for enabling the switch to' perform another operation, a change over circuit for transferring the action of the said controlling relay from the primary circuit to the secondary circuit, a change over electromagnet in the change over circuit, a front contact on the said controlling relay and a back contact on the change over electro'niagnet for closing the change over circuit,-and an off-normal contact included in the change over circuit that is closed only when the said switch is in an off-normal position.

function, said change over relay receiving current durlng the travel of the armaturev of the control relay from its one position to its other position.

In witness whereof I have signed this specification in the presence of two witnesses.

FRITZ ALDENDORFF. Witnesses:

HENRY HAsPER, WOLDEMAR HAUPT. 

